1. Field of the Invention
This invention relates to an inkjet printing apparatus, and more particularly to a technology of preventing a drop of ink from an ink leading-out needle, which is possibly generated at the time of pulling an ink tank out of an ink tank holder.
2. Description of the Related Art
As means of supplying ink to a print head in an inkjet printing apparatus, there is provided a pressure supply system of pressurizing the ink in an ink tank or an ink flow passage by a pump or a water head pressure to supply the pressurized ink to the print head.
According to this system, in a case where an amount of the ink in the ink tank is reduced or a quality assurance period of the ink is expired, an appropriate ink supply state can be recovered by replacing the ink tank.
On the other hand, in this system, the ink possibly drops at the time of pulling the ink tank out of the ink tank holder. That is, an ink leading-out needle, which can lead out the ink in the ink tank to the ink flow passage in the inkjet printing apparatus when the ink tank is mounted onto the ink tank holder, is provided at the ink leading-out portion of the ink tank or on the ink tank holder, wherein, the ink tends to easily drop from a tip end of the ink leading-out needle at pullout of the ink tank. This is because the ink between the ink tank and the ink tank holder is pulled and separated by each member to drop or the ink pooled in a tip end of each member drops due to an impact at pullout or the like.
For overcoming this problem, there is known a method where a pressurized pressure relief mechanism is activated to return an ink pressure in the ink flow passage back to an atmospheric pressure, and then the ink tank is pulled out, thus reducing an amount of the ink droplets. Also in this method, however, there are some cases where components such as resins or rubber constituting the ink flow passage, which are deformed or expanded by pressures, or metallic films will be back to original dimensions with time, and therefore a small deal of the ink drops from the ink leading-out needle after ink tank pullout.
When the ink thus drops, the ink is attached to the inside of the ink tank holder and is then attached to a housing peripheral portion of the ink tank. Therefore, there are some cases where hands of an operator get dirty or in a case where a pullout sensor is attached to the ink tank, an erroneous operation occurs. As the measure technology on this problem, there is known a method where a valve operable in association with pullout of the ink tank is provided in a printing apparatus body or a technology disclosed in Japanese Patent Laid-Open No. 2008-049640. In detail, in Japanese Patent Laid-Open No. 2008-049640, an absorbent is provided in the periphery of the ink leading-out portion of the ink tank and the dropped ink is retained by the absorbent. Therefore, there is no possibility that the hands of the operator get dirty.
However, the construction of providing the valve mechanism to the printing apparatus body leads to an increase in size or in cost of the printing apparatus. Further, the construction of providing the absorbent in the periphery of the ink leading-out portion of the ink tank as in the case of Japanese Patent Laid-Open No. 2008-049640 brings in an increase in cost due to the provision of the absorbent. In addition, there is a possibility of damaging sealing properties of a sealing member provided in the ink leading-out portion for preventing leakage of ink, due to dusts generated from the absorbent.